Fluorination of 2<i>H</i>‑Indazoles Using <i>N</i>‑Fluorobenzenesulfonimide

An efficient, simple, and metal-free
fluorination of 2H-indazoles has been developed using N-fluorobenzenesulfonimide
(NFSI) in water under ambient air. This transformation provides direct
access to fluorinated indazole derivatives with broad functionalities
in satisfactory yields. The experimental results suggest a radical
mechanistic pathway of this protocol.